A heat pump that has been known to date includes an accumulator disposed near a suction port of a compressor and allows refrigerant returning to the compressor to pass therethrough (e.g., Patent Literature 1, hereinafter referred to as PTL 1). The accumulator separates liquid refrigerant from gas refrigerant returning to the compressor to thereby suppress a flow of the liquid refrigerant into the compressor.
The heat pump described in PTL 1 is configured to gasify liquid refrigerant in the accumulator and return the gasified refrigerant to the compressor. Specifically, the heat pump includes a refrigerant return channel connecting a refrigerant channel between the compressor and the accumulator to a bottom portion of the accumulator. The refrigerant return channel is provided with an expansion valve that reduces the pressure of liquid refrigerant and a heat exchanger that gasifies the liquid refrigerant whose pressure has been reduced by the expansion valve. The heat exchanger gasifies liquid refrigerant whose pressure has been reduced by using high-temperature cooling water of an engine that drives the compressor. In this manner, liquid refrigerant in the accumulator is gasified and returned to the compressor to be reused.